Rats and mice and their relatives in the order Rodentia make up almost half of the species of mammals. Because of this, we polled our readers and the overwhelming positive response was to produce two volumes treating Rodents. Volume 6 will include all of the families of rodents other than Cricetidae and Muridae, plus the order Lagomorpha, which includes rabbits and pikas. This radiation includes some 35 families, which have spread around the globe, occupying every continent except Antarctica, and countless islands in all major oceans.